Pressure fluid supply system



, Oct. 13, 1953 D; N. WALKER 2,655,109

PRESSURE FLUID SUPPLY SYSTEM Filed May 5, 1945 INVE NTOE Patented Oct. 13, 1953 UN I TE D vS TAT ES Q'FiF I CE R SS RE i-Iim SUB LYSX TEM "Daniel Nz-walker, Ashby Parva, nearRugby, England, assignor to-Power Jets atResearch & aDevelopment) Limited, London, England Ap lic ion Ma -.3, 1 e ialtN laatu 15111 G setB f lMe wlflli .1 :Claim. '1

This invention relates to pressurefluid supply systems and in particular to systemsin which it is required to supply fuel for example to an aero engine under substantialpressure. Some classes ofengine are dependent upon a pressure fuel supply for their operation, for example engines of the gas turbine class. Such engines comprise .a compressor driven by a turbine mounted coand the mixture ignited,the hot gases then being led to the turbine thus driving it, and beingv subsequently emitted to atmosphere. Inthe interest of reliability of operation it-may be considered desirable to provide a system-such that if a pump failure should occur the engineis not tobe out of action and it is also found desirable at least in connection withgas turbine engines to provide a fuel system such that for starting purposes a rate of supplyis available (at comparatively low pressure) which would require a-larger capacity pump than is necessary for normal running after starting. Thepresent invention seeks to provide a pressure fluid supply system -'in which dual pumps are afforded which meet the requirement of reliability and in which a comparatively large capacity is available for exampleto meettherequirements of starting a gas turbine engine. It is assumed in the following description that the pumps are mechanically driven by'the engine itself although there may be cases where they are independently driven.

-ing element and its non-return valve to the common suction conduit, a pressure actuated -flow control valve means in't he by-pass conduit for controlling the flow therein, and a pressure conduit connecting the discharge branch of the other pumping element from a point between the pumping element and its non-return valve tothe pressure actuated flow control valve means for "supplyin it with pressure fluid from the other pumping element-to actuate itpthe'valve means --being biassed to close the by-pass conduit when the dischargepressure ofthe other pumping elementis-below a predetermined value to permit the pair of pumping elements to pump in parallel anddisoharge fluid to the common discharge conduit andthe valve means being actuated' by the pressure fluid when the discharge pressure of the otherpumping element is above the predetermined value to open the by-pass conduittoypermit-the one pumping element to discharge "fluid to thecommon suction while the other pumping element continues to discharge fluid to thecommon discharge conduit. 'In'the event of failure of the other pumping element, the biassin 110241 on the pressure actuated flow control valve means cause'sitto close the by-pass conduit and the one pumping element commences to pass fluid to the common discharge.

Theinvention will be better understood from the following description of one form of embodinent of the invention which is given byway of example with reference to the accompanying drawings in which: 7

.Fig. 1 is a diagrammatic representation of a system according tothe invention with the pressure actuated fluid flow control valve means d ed "Fig'. 2 is a similar representation of the same systemwi h the p ssure. c ated fluid flow o o valve means j Referring to the drawings, thesytem according to the invention comprises twopumps A, B, for delivering fluidvunder pressure, the fluid being led from a source of supply through a main sue tion pipe connection I.

A-branch pipe 2 is connected to pipe I and leads to the suction side of pump B, the delivery ,side of this pump 'being connected through a pipe 3'to a non-returnvalve l and thence by a pipe ii to a pipe i2 for delivery of the fluid to anapp-aratus.

Pipe Lleadsto the suctionside ofipump A of whic th d i rysidele d t ou h pipe. H t a nonereturn valve. 8 and thence through pipe l2 .to the apparatus wherein the delivered fluid is tobe used.

Connectedto pipet is a branch pipe 4 leading t rcu et o e n to the amb 16 of a pressure actuated flow. control valve means c ns stin o a ca n i c o n a cham e HS in which slides a piston valve l3 against the resistance, of a springl l. he chamber It can qommuniq t thrqes a pa and a pi e It hec -"t thema s et q Pi eepin len l0 constituting a main bypass conduit. The

chamber [6 is connected by an opening 22 to a pipe in communication with the pipe II and an opening 2| and pipe 9 which serves as a drain in a manner which will be hereinunder described, link the chamber [6 to the suction pipe I.

A bleed line 20 is provided in the piston valve l3. An annular groove I9 is provided on the piston valve l3 to provide a passage for the fluid passing from the pump B when the lateral opening I! is uncovered by the piston valve l3.

Fig. 1 represents the condition of the system when for example it is desired to start a gas turbine engine in which combustion is efiected by means of burners (not shown) to which pipe I2 is connected for the delivery of fuel. The spring i4 is designed to yield at a certain predetermined pressure so that when the pressure of the fluid discharged by the pump A is less than'this value, the pressure actuated flow control valve means is closed and there is no communication between ports I! and i8, but when this pressure is exceeded, then the piston valve I3 is moved against the spring l4 and by means of the annular groove l9, ports I1 and It can then communicate with one another.

For starting conditions, the pressure actuated flow control valve means is closed as shown in Fig. 1 and pumps A and B are in this case operating in parallel. As indicated by the arrows which show the path of the liquid, pump B is supplying fuel via pipe 3, non-return valve 1 and pipe 5, while pump A delivers fuel through pipe I I, nonreturn valve 8 and pipe l2 to the burners. The pressure of the fuel delivered increases until it reaches the given pressure and when this value is reached the piston valve l3 moves against spring i4, thus putting ports ll and I8 and consequently pipes 4 and In in communication with one another, as shown in Fig. 2. In this condition, as shown by the arrows, pump B circulates fuel idly and is operating on substantially no load while pump A continues to deliver and is alone responsible for delivering substantially all the fuel required at the desired pressure. The nonreturn valve l prevents pump A from delivering liquid back to suction via the pressure actuated flow control valve means.

If pump A fails, the pressure in its delivery line i 1 drops and the piston valve IS in the pressure actuated flow control valve means then moves back to the position of Fig. 1, thus cutting off communication between the delivery side of pump B and pipe I. As shown by the arrows, pump B then delivers fuel through pipe 3, non return valve 7 and pipe 6 to the burners and is then itself responsible for delivering all the fuel at the required pressure.

If pump B fails while A is operating under load, then the system remains otherwise unaffected and pump A continues to deliver.

As the flow through a failed pump may in some cases be relatively small, a bleed line 20 is provided in the piston valve I3 of the pressure actuated flow control valve means in order to promote a rapid changeover. A lead 9 to drain is also provided in the said valve for the purpose of permitting leakage through the piston valve [3 to drain back to source and thus prevent any possibility of such leakage building up a pressure which together with the force exerted by the spring H on the piston valve l3 may operate to close the pressure actuated flow control valve means when this is required to remain open.

The pumps A and B are of the positive displacement type and they may be gear pumps actually driven from the engine shaft for example in the case of a gas turbine aero engine. Relief valves may be provided in association with any part of the system where the possibility of excess pressure may arise and the non-return valves may have associated with them any suitable signalling device to give an indication of the operative condition of the system at any one time.

One method of arranging such a signalling device is shown in Fig. 1. A pressure gauge 32 is connected bymeans of piping 33 to pipe 3 and the pressure in said gauge is indicated by a pointer 34 adapted to make electrical contact when the pressure is above a certain value with contact 25, and when the pressure is below another .value with contact 24. A battery 26 is connected through a circuit 21 to a lamp 28 and also through a circuit 29 to a lamp 3E1 so that one of these lamps will light according to whether the pointer 34 is in contact with contact 25 or contact 24. When pump A fails the pressure in pipe 3 will exceed the value corresponding to contact 25 so that in this case pointer 34 will move over to said contact 25 and lamp 28 will light. Similarly if pump B fails, the pressure in pipe 3 will fall b low the value corresponding to contact 2 2 and in this case lamp 30 will light. These lamps may be of difierent colours or otherwise suitably distinguished, and the illumination of one or other of the lamps will then indicate that either pump A or pump B has failed.

The pressure actuated flow control valve means may be provided with means such as spring loaded toggle linkage to give the valve a snap action so that it is held in one or other of its positions until there is a substantial change of conditions, flutter of the valve thus being avoided. Alternatively the valve may be operated electrically for example by a solenoid in a circuit which is itself affected by the operating conditions. Yet again the valve may be interconnected with a throttle or other user-controlled element so as to efiect the changeover at some particular phase of use, and when the valve is manually operated, arrangements may be made whereby the valve is inevitably closed (i. e. returned to the parallel condition) if the main fuel supply be shut oil as in closing down an engine. a Y

I claim:

A pressure fluid supply system including a pair of pumping elements for continuous operation, a common suction Conduit and a common discharge conduit having suction and discharge branches respectively connecting said pumping elements in parallel for parallel suction and parallel discharge flow, non-return valves in both said discharge branches for permitting flow only in the direction of discharge, a main by-pass conduit connecting the said discharge branch of one of said pumping elements from a point between said one pumping element and its said non-return valve to .said common suction conduit, a pressure actuated .fiow control valve means in said by-pass conduit for controlling the flow therein, and a pressure conduit connecting said discharge branch of said other pumping element from a point between said other pumping element and its said non-return valve to said pressure actuated flow control valve means for supplying it with pressure fluid from said other pumping element to actuate it, said valve means being biased to close the said bypass conduit when the discharge pressure of said other pumping element is belowa predetermined value to permit said pair of pumping elements to pump in parallel and discharge fluid to said common discharge conduit and said valve means be ing actuated by said pressure fluid when said discharge pressure of said other pumping element is above said predetermined value to open said bypass conduit to permit said one pumping element to discharge fluid to said common suction while said other pumping element continues to discharge fluid to said common discharge conduit.

DANIEL N. WALKER.

References Cited in the file of this patent UNITED STATES PATENTS Number Number Number Name Date Perkins Sept. 5, 1911 Rosencrans July 27, 1915 Johnson July 6, 1937 Egersdorfer et a1. Sept. 19, 1939 Vickers Oct. 22, 1940 Jung Oct. 29, 1940 Herman et a1. Apr. 21, 1942 Crosby Jan. 2, 1945 Wheatley Jan. 16, 1945 FOREIGN PATENTS Country Date Germany 1938 France 1931 

